A GLOBAL H2O POTENTIAL-ENERGY SURFACE FOR THE REACTION O(D-1)-2-]OH+H(H)

A global, single-valued ground-state H2O potential surface for the rea ction O(D-1) + H-2 --> OH + H has been constructed from a new set of a ccurate ab initio data using a general multidimensional interpolation method. The ab initio calculations are of the multireference, configur ation interaction variety and were carried out using augmented polariz ed triple zeta basis sets. The multidimensional method is formulated w ithin the framework of the reproducing kernel Hilbert space theory. Th e H2O potential is expressed as a many-body sum of a single one-body t erm, three two-body terms, and a single three-body term. The one-body term is the dissociation energy to the three-atom limit 2H(S-2) + O(P- 3). The two-body terms are two O-H and one H-H adiabatic diatomic pote ntials of lowest energy. Each diatomic term is obtained by interpolati ng a discrete set of ab initio data using a one-dimensional, second-or der, distancelike reproducing kernel. The three-body term is obtained by interpolating the difference of the H2O ab initio data and the one- and two-body sum by means of a direct product of three one-dimensiona l reproducing kernels on an optimized regular three-dimensional grid. The H2O potential energy surface is accurate, globally smooth, easy to evaluate, and asymptotically correct. Extensive quasiclassical trajec tory calculations based on this new potential energy surface have been performed and compared with the results based on the potential energy surface of Murrell and Carter (MC) and that of Schinke and Lester (SL ). Comparisons with recent experimental measurements on total cross se ctions, isotope effects, rate constants, vibrational, rotational, and angular distributions of the O(D-1) + H-2/HD reaction show that the ne w potential energy surface is a significant improvement over the MC an d SL surfaces. (C) 1996 American Institute of Physics.